A semiconductor thin film of polycrystalline silicon (poly-Si) and so on is widely used for a thin-film transistor and a solar cell. As a method of forming the semiconductor thin film inexpensively, there is a method in which an amorphous silicon film is irradiated with a laser light to crystallize the film. The laser process can be applied to activation of impurity atoms introduced to a semiconductor substrate by ion implantation or plasma doping. However, there are problems that the attaining temperature varies due to the amount of light absorption of an object to be heated and that a joint is generated in the laser annealing technique, and extremely expensive equipment is necessary.
In response to the above, a technique in which a linear thermal plasma is generated in the vicinity of the substrate, and scanning is performed only in one direction to thereby perform heating not depending on light absorption of the object to be heated and realize thermal treatment seamlessly and inexpensively is considered (for example, refer to JP-A 2013-120633: (Patent Document 1), JP-A 2013-120684 (Patent Document 2), JP-A 2013-120685 (Patent Document 3)) and Non-Patent Document 1).    [Non-Patent Document 1] T. Okumura and H. Kawaura, Jpn, J. Appl. Phys, 52 (2013) 05EE01